1. Field of the Invention
The invention relates to steam-flaking grain for animal feed. Specifically it relates to a method for reducing the variability in the amount of gelatinization of steam-flaked grains.
2. Statement of the Problem
Grain has achieved popularity as a feed grain for feeding cattle both on feed lots to provide meat and in dairies for milk production. It has been found that the efficiency with which cattle can convert grain into weight gain or increased milk production can be enhanced by treating the grain prior to feeding. Even minute increases in feed efficiency will result in substantial dollar savings. For example, an average improvement of 6% from correctly steam-flaking corn potentially realized an estimated $750,000 to $1.5 million annually on 30,000 head of feedlot cattle.
A number of processes have consequently evolved for treating feed grain to increase the digestive efficiency of the grain. The digestive efficiency of grain can be increased by transforming the starches in the grains to more digestible compounds. The greatest increase in digestive efficiency has been obtained by the steam flaking process in which feed grain (such as corn, sorghum, wheat and barley) is subjected to steam in a closed steam chest at various pressures and times during which the grain absorbs moisture from the steam. The grain is then fed between pressure rollers to provide thin flakes. The improved digestive efficiency achieved by this process results from the fact that the moisturization, heat, and flaking gelatinizes (solubilizes) some of the starch granules of the grain so as to render them more digestible by cattle.
The main purpose for steam-flaking grain is to increase starch digestibility thereby maximizing net energy intake by cattle and subsequent performance. To achieve this, approximately 40% to approximately 60% (preferably about 500 to about 750 lb/ton of dry grain) of the starch in properly steam-flaked corn, for example, should be gelatinized compared with only 35% or less for steam-rolled or poorly steam-flaked grain. Grains low in gelatinized starch content can negatively impact profitability unless price is adjusted to offset the reduction in animal performance. Tables I and II illustrate the value of steam-flaked compared with steam-rolled corn in terms of gelatinized starch content and milking performance.
Thus, when grain is properly steam flaked (i.e., preferably about 56% gelatinized), milk production typically increases 5 to 6% compared with steam-rolled or poorly steam-flaked grain. Overall animal production (i.e., weight gain, milk production, and feed efficiency) was improved 5% to 16% when steam-flaked grains were fed compared with steam-rolled, dry-rolled, and ground forms of grain.
Improved animal performance by feeding steam-flaked grain is largely due to increased digestible energy intake from increased starch digestibility. During steam-flaking the starch in grain becomes gelatinized which increases its susceptibility to enzymatic and bacterial degradation in the ruminant (e.g., beef and dairy cattle) digestive tract. In ruminant animals the majority of starch is degraded in the rumen with a small amount passing through to the small intestine. The rate and extent to which ruminal starch digestion occurs is strongly influenced by the gelatinized starch content (i.e., processing degree) of the steam-flaked grain. Highly processed grains contain a high percentage of gelatinized starch that is rapidly degraded in the rumen. Feeding grain containing excessive amounts of gelatinized starch has been shown to depress animal performance or cause death due to digestive upset, acidosis, depressed feed intake, founder, and depressed digestibility of other nutrients, and it also increases milling costs. Under processing grain can increase the cost of animal production (if grain price is not appropriately adjusted) because reduced starch digestibility results in depressed feed efficiency.
To minimize the negative affects of under- or over-processing grain while at the same time improving efficiency of animal production, careful consideration should be given to each and every condition that is imposed during the steam-flaking process. Factors most strongly influencing conversion of starch to gelatinized starch are water, temperature, time, flake density, and grain quality. Starch will gelatinize (i.e., melt) when it is heated in the presence of water for a given period of time. As temperature rises water will penetrate the starch granule causing a change in its structure indicated by a loss of birefringence; by definition this is gelatinization. To permanently gelatinize the starch granule, cooking temperature, moisture, and mechanical force/pressure must work in combination to fracture it. If the granule is not fractured, upon cooling it will lose water and retrograde to a highly uniform structure.
Retrograded starch is lower in digestible energy compared with intact starch because it is extremely resistant to enzymatic and bacterial degradation.
Currently, there are no industry standards or indices that are followed to commercially produce steam-flaked grains for livestock with the explicit purpose to gelatinize starch to a targeted predetermined level and that minimize variability in the amount of gelatinization.
3. Solution to the Problem
In an effort to improve the efficiency of animal production and profitability of the livestock industry, a goal that has been long sought by the industry, the present invention comprises a unique method for commercially producing steam-flaked grains for the specific purpose of achieving targeted predetermined levels of gelatinized starch.
It is an object of the present invention to provide a method of steam-flaking grain that optimizes the amount of gelatinization in feed grain during the on-going processing of the grain.
It is a further object of the present invention to provide a method of steam-flaking grain that provides a predetermined level of gelatinization while minimizing variance in the amount of gelatinization during the steam flaking process.
The method of the present invention for steam flaking grain comprises in general the steps of providing grain, passing the grain through a steam chest at a predetermined temperature and pressure for a predetermined time, flaking the grain by passing it through a predetermined gap between two rotating corrugated rollers, sampling the flakes at predetermined intervals as the flakes come out from between the rollers, cooling the sampled flakes, weighing the sampled flakes to determine the density of the sampled flakes, and adjusting the temperature, the pressure, the retention time, and the size of the gap between the rollers on the basis of the measured density of the sampled flakes, so that the resulting flakes have a predetermined density and a predetermined amount of gelatinization. The method of the present invention thus minimizes the variability in the amount of gelatinization in the resulting steam-flaked grain.